Photocatalysis of the Reduction of Cd2+ Ions by CdS Nanoparticles in Isopropyl Alcohol

The kinetic relationships governing the photocatalytic reduction of Cd²⁺ cations with participation of CdS nanoparticles in isopropyl alcohol solutions were investigated. Quantum-dimensional effects that manifest themselves in an increase in the rate of the process with decrease in the average size of the photocatalyst nanoparticles were observed and interpreted. In the light of published data a scheme that agrees satisfactorily with the experimental results is proposed for the mechanism of the photocatalytic reduction of cadmium ions.     

Features of formation of CdSe nanoparticles in aqueous sodium polyphosphate solutions

A study was carried out on the features of formation of stable aqueous colloidal solutions containing CdSe nanoparticles stabilized by sodium polyphosphate resulting from a reaction between cadmium chloride and sodium selenosulfate. The major parameters determining the size of the CdSe nanoparticles are the reaction medium temperature and the ratio of the starting reagent concentrations. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 2, pp. 102–106, March–April, 2006.     

Photocatalysis of the Release of Molecular Hydrogen from Aqueous Solutions of Sodium Sulfite by Composite CdS/Ni Nanoparticles

The photocatalytic reduction of Ni²⁺ cations at the surface of CdS nanoparticles was investigated. It was found that the CdS/Ni nanocomposite formed as a result of the reaction exhibits photocatalytic activity in the release of molecular hydrogen from aqueous solutions of sodium sulfite. The kinetic relationships of the process are studied, and a mechanism for the studied reactions is proposed.     

Thermophysical study of structural phase transitions in Na<Subscript>0.95</Subscript>Li<Subscript>0.05</Subscript>NbO<Subscript>3</Subscript> solid solution

Temperature dependences of specific heat C_p(T) and coefficient of thermal expansion ;(T) for Na_0.95Li_0.05NbO₃ sodium-lithium niobate ceramic samples are investigated in the temperature range of 100–800 K. The C_p(T) and α(T) anomalies at T₃ = 310 ± 3 K, T₂ = 630 ± 8 K, and T₁ = 710 ± 10 K are observed, which correspond to the sequence of phase transitions N ? Q ? S(R) ? T2(S). The effect of heat treatment of the samples on the sequence of structural distortions was established. It is demonstrated that annealing of the samples at 603 K leads to splitting of the anomaly corresponding to the phase transition Q → R/S in two anomalies. After sample heating to 800 K, the only anomaly is observed in both the C_p(T) and ;(T) dependence. Possible mechanisms of the observed phenomena are discussed.     

Effect of cavitational disintegration of surplus activated sludge on methane generation in the process of anaerobic conversion

The effect of mechanical pretreatment of surplus activated sludge from the wastewater treatment facilities of a plant producing chips (LLC “Frito Lay Manufacturing,” Kashira, Moscow oblast) in a cavitation disintegrator on methane generation in the process of anaerobic conversion is investigated. In laboratory conditions, cavitation disintegration pretreatment of the activated sludge results in a two- to sixfold increase in the transfer of various types of organic materials from the cell suspension into the aqueous phase. It is demonstrated that cavitation pretreatment of the activated sludge makes it possible to produce 31% extra methane as compared to the amount produced from the original sludge.     

Optical and electroluminescent characteristics of CdS nanoparticles stabilized by guanidine-containing dendrimers

Colloidal CdS nanoparticles measuring 1.9-2.3 nm and stabilized by guanidine-containing dendrimers were produced. It was established that such nanoparticles are characterized by photoluminescence in a wide spectral range (2.1-3.2 eV) with an average radiative lifetime of 55-85 ns depending on the energy of the emitted quanta and also by electroluminescence in the visible region of the spectrum (1.8-2.8 eV).     

Dynamics of the radiative recombination of charge carriers in CdS nanoparticles stabilized with polyethyleneimine

The dynamics of the radiative recombination of charge carriers in CdS nanoparticles stabilized in aqueous solutions of polyethyleneimine was studied. It was shown that decay of the photoluminescence of the nanoparticles is characterized by a set of time constants in the range of 10⁻¹-10²ns, while its rate depends on the energy of the radiation quanta. This relationship is interpreted as the result of competition between the processes of radiative recombination and vibrational dissipation of the excitation energy.     

Effect of CH4/Air Ratio on Selectivity of Partial Oxidation of Methane on V2O5/SiO2 Catalyst

We have studied partial oxidation of methane on V₂O₅/SiO₂ (0.8 mass % V) in a flow-through catalytic fixed-bed reactor. We found that the methane/air ratio in the starting reaction mixture has practically no effect on the selectivity of the process. The dependence of the selectivity on the methane conversion can be described by a model with such reaction parameters as the initial selectivity and the relative reactivity (with respect to methane) of the reaction products.